1. Field of the Invention
The present invention relates to a chair with a pivoting backrest capable of tilting backwards under a thrust applied by the user's back.
2. Description of Prior Art
In the state of the art, there are various known solutions of chairs in which the backrest is connected to a fixed support structure by a pair of elastic joints, each of which comprises an upper support inserted into a tubular portion of the backrest, a lower support inserted into a tubular element of the fixed support structure and an elastic element, which allows an inclination between the upper support and the lower support.
For example, the document EP2183997 of the same applicant describes a chair comprising a base structure including two rear tubular elements, a backrest having two tubular portions and two elastic devices, each of which has an upper support inserted into a tubular portion of the backrest, a lower support inserted into the corresponding tubular element of the base structure and an elastic element deformable by bending to allow pivoting between the upper support and the lower support, wherein each of the elastic devices comprises a plurality of stacked sectors, arranged between the upper support and the lower support.
The elastic elements that are deformable by bending have the drawback of a limited elastic force for opposing the backward thrust applied by the user.
In principle, with elastic elements in compression formed, for example, by helical compression springs, it would be possible to increase the force provided by the elastic joints that contrast the backward thrust applied by the user on the backrest of the chair. However, with helical compression springs arranged coaxially to the side uprights of the backrest, the lever arm for the compression of the springs is limited.